Color tube, control system



Jan- 12, 1960 J. w. SCHWARTZ coLoR TUBE, coNTRoL SYSTEM Filed 001;. 26, 1954 IN VEN TOR.

/l Tros/v5 y TLV COLOR TUBE, CONTROL SYSTEM James W.v Schwartz, Princeton, NJ., assig'nor to Radio Corporation of America, a corporation of Delaware Application October 26, 19,54, Serial No. 464,744

6 claims. (cl. vs -5.4)

This invention relates to a color television system and more particularly to methods and arrangements for reproducing images in substantially their natural color;

Y It has been previously proposed to produce an image in color by causing a single beam of electrons to impinge. repeatedly upon different component color light'producing elements on a target electrode. The beam of electronsis then sequentially intensity modulated with dierentfcolor signals, in synchronism with the sequential excitation by the electron beam of the component color light producing elements. To properly reproduce an image in this manner it is necessary that there be color coincidence i.e synchronization between the intervals of modulation during which the electron beam is intensity modulated with a particular component color signal, and the intervals of excitation, during which the target electrode is producing a particular componentcolor. j

It has been proposed to position certain signal'generat` ing elements upon the target electrode which will cause a signal to be generated as the target electrode kis scanned by an electron beam. The signal generating elements may take any of several forms including arrangements wherein they are composed of secondary emissive material, of photo emissive material, of conducting material,`

or void of any electron beam responsive material with the remainder of the target composed of material responsive to electron beam energy. The-fact that thehsignal from the signal generating elements is indicative of beam position with respect to thetarget electrode, enables'utilization of this signal to control the relationship between the intervals of modulation and the intervals of excitation. The target generated signal from the signal generating elements may contain random false impulses resulting from the varying electron beam intensity as the electron beam scans the target electrode and from spurious signals injected into the target generated signal.

With the object of creating a more uniform target generated signalv it has been previously proposed to cause the electron beam to be substantially constant during the intervals when the signal generating elements are excited. As a result the target generated'signal is not dependent upon the magnitude of the video signal intensity modulating the electron beam. Exciting the signal generating elements by a periodically essentially constant intensity electron beam, however, does not entirely remove the spurious and random impulses from the target'generated signal, other impulses are, for example, created by pickup from the varying energy content of the electron beam.

In its more general form the present invention contemplates a method and apparatus for the essential elirnination of random false impulses from a target generated signal, generated by an electron beam scanning a target electrode, and utilized to control the electron beam.' The target generated signal may be formed by causing an -elec tron beam to periodically impinge upon signal generating elements substantially during intervals when the intensity of the electron beam is essentially constant. A gating cir- Gitti iPlae@ *11e ya@ Qf the targetrgenerated signal atent f, ice

. which will allowthe passage of the target generated signal only during the intervals when the electron beam intensity is essentially constant which interval coincides with the intervals during whichthe target signals are formed.

Anobject of this invention is to provide an improved color television image reproducing system.

Another object of this invention is to provide a system in which a target generated signal generated by causing an electron beam to scan a target electrode, is essentially free of random impulses.

A further object of this invention 1s to provide a color 1i television system wherein a target signal is generated by an electron beam scanning a target electrode and used to effect correct color reproduction, issubstantially free' of spurious impulses. v

. Other and incidental objects of this invention willlbe "l apparent to those skilled in the art from reading the fol-v lowing specification and on inspection of the accompanying drawings in which:

The single figure of the invention shows a blockV and circuit diagrammatic representation of a system of the invention..

' In the igure there is shown a color television receiverl 10 for generating three color output signals7 each representative of a component color, a red signal R, a blue signal B and a green signal G. Such a receiver is shown and described in a series of articles entitled Fundamentals; of`Color Television which appeared in Radio Television;

News, beginning March 1954, and were written by Mil@ ton S. Kver.

The color output signals from the color television rej ceiver 10 are connected to deliver the green signal GV to a sampling circuit 12, the blue signal B to a sampling cir-l cuit 14, and the red signal R to a sampling circuit 16. The sampling circuits 12, 14 and 16 plus an additional sampling circuit 1S are connected so as to sequentially4 pass signals to an adder circuit Ztl in such a manner that the outputs of the sampling circuits 12, 14, 16 and'. 18 will be combined in the adder circuit 20 to form a; composite signal. The composite signal from the adder circuit 20 is connected to be applied to a cathode 22 of an image reproducing tube 24. The image reproducing tube 24 is provided with a target electrode 26. The target-,p

electrode 26 comprises groups of component color light producing strip-like elements 28, 30, 32 and 34. The

strip-like elements 28, 30 and 32 are composed respec-- lPositioned exterior to the image reproducing tube 24 is Y a photoelectric device 36. Separating the photoelectric device 36'frorn radiation sources within the imagereproducing tube 24 is an ultra violet light passing lilter 38. The electrical target generated signaloutput from the photoelectricy device 36 is connected to an amplifier 411i and-thence, after ampliiication, to a gate circuit 42. i r

The gate circuit 42 consists of a vacuum tube 44 adapted to receive two input signals.V Oneof the input signals to the vacuum tube 44 is applied to a grid 46 through an input circuit 48, the other input signal i. e., the target generated signal is applied to a grid 5t) through an input circuit 52. The output of the vacuum tube 44 from a plate electrode is serially connected to a group of delay circuits 54, 56, 58 and 60. Each of the delaycircutsy 54, 56, 58 and 60 are respectivelyconnected to control the sampling circuits 12, 14 and 16 are adapted to gate the color signals R, B, and G to the adder circuit 20, the sampling circuit 18 is connected to a potential source 62 such that the function of the sampling circuit 18 is to periodically sample i.e., gate a substantially constant voltage to the adder circuit 20.

In regard to the operation of the system shown in the figure, the three color signals R, G, and B from the color television receiver are each representative of the'intensity of component color light to be reproduced in a televised image. The function of the sampling circuits 12, 1,4, 16 and 18 is to. sequentially operate to form a composite signal. During different intervals the composite signals is sequentially representative of different of the color signals R, B, G orthe substantially constant voltage. The composite signal formed in the adder circuit 20, is utilized to intensity modulate an electron beam in the image reproducing tube 24, by application of the composite signal to the cathode 22. Y

As the intensity modulated electron beam is deected over the target electrode by means of the deflection coils 25, the excitation intervals during whichv the electron beamv impinges upon each of the strip-like elements 28,.y 30, 32 or 34 must coincide with the modulation intervals during which the electron beam is modulated respectivelyby Acertain of the signals R, B,`G or the substantially constant signal. During the interval when the electron beam is intensity modulated'by the red signal R, for example,

the electron beam must be impinging upon the strip-like elements 28 which will produce red light when excited by the electron beam. Similarly, during the interval. when.

the bluev'light is being reproduced, i.r e., the electron beam Y is impinging upon the blue light producing strip-like ele- Vments 30, the electron beam should be modulated by the blue signal B. During the time when the electron beam should be intensity modulated by the green signal G, the electron beam must impinge upon the green light producing strip-like elements 32. During the excitation intervals when the ultra violet light producing. strip-like elements 34 are excited, the electron beam should be held at a substantially constant level thereby eliminating the video signals from the target generated signal generated by the electron beam Vitnpinging upon they elements 34.

VThe photoelectric device 36 primarily receives the tart get generated signals of ultra violet light radiated from the strip-like elements 34. The target generated-,signals sensed by the photoelectric device 36 are amplified by the amplifier 40 and applied by means lof the input circuit 52 to the grid electrode 50 of the electron tube 44. The input circuit 48 which is connected to receive a gating signal from sampling circuit 18, will receive such a gating signal only during the interval when the electron beam is at a predetermined substantially constant level, that is,

not modulated by video signals. It is during this constantV beam interval that the ultra violet light producing elements red signal R, and a substantially constant voltage from the potential source 62. The time delay of the delay circuits 54, 56, 58 and 60 is so arranged that the electron beam will be intensity modulated by a color signal which coincides in color with the color of light produced by the light producing elements on which the electron beam is instantaneously impinging;

During the normal operation of an arrangement of this type random impulses will be picked up by the photoelectric device 36 during intervals otherV than those which are'- utilized to excite theultra violet light producing phosphor elements 34, however, with the provision of the gating circuit 42 a substantial part of such random impulses will 'Y be eliminated and the circuit will tend to be less likely 1. A system for controlling an electron beam compris ing a target electrode having signal generating elementsV positioned thereon, said signal generating elements for developing a target generated signal as said target elecdv trode'is scanned by an electron beam, means for producing an electronV beam for scanning said target electrode,

i means for Vcausing said electron beam to maintain a substantially constant intensity during excitation intervals substantially only when said electron beam excites said signal generating elements,.sensing means for sensing saidtarget generated signal. to form an'electricaltarget gen-v erated.. signaLgating meansy for allowing 4the passage of said electrical target generated signal substantially only during said excitation-interval to form a gatedv electrical target generated signal, and means for utilizing said gated electrical target generatedV signalV to control the phase relation ,between the modulation of said electron beam and the position of said electron beam.

2. A color television system1comprising a target electrode having signal generating elements positioned thereon, said signal generating elements for generating a target generated signal upon being excited by electron beam energy, means for generating an electron beam for scanning vsaid target electrode, means for establishingthe intensity of said electron beam at a substantially constant level durf ing predetermined intervals, said predetermined intervals being such as to substantially coincide in time with and occur substantially only during excitation intervals duringY which saidjelectron beam excites said signal generating elements, sensing means for sensing said target generated signal from said signal generating elements to :forman electrical target generated. signal, gating means for pass` ingsaid. electrical signalsubstantially only during said ex- 34 are to be excited, and therefore during this constant V beam interval at the target generated signal sensed by the photoelectric device 36 is desired to be received. =It may therefore be seen that the gate circuit 42 with the periodio application of the gating signal to the grid 46 of theelectron tube 44, will periodically allow the .passage of the target generated signal. The gating signal will occur only during the interval when the electron beam is essentially constant thus only during this interval will the.

target generated signal pass the gate circuit 42. The gated target generated signal passing through the gate circuit 42 isvdelayed, by various predetermined amounts in the delay circuit 54, 56, 58 and 60.

respective sampling circuits 18, 16, 14 and 12 are each phase shifted in such a manner as to be essentially 90 apart. Upon receiving the phase shifted signals, the

The signal outputv from each of the delay circuits 54, 56, 58 and 60 to theY citation intervals Yto forma gated electrical target generated-signal, and means for utilizing said gated electrical target generated signal to control the phase relation between the modulation of said electron beam and the position of saidr electron beam.

3. A color television'system comprisinga target elec-V Y trode having signal generating elements positioned thereon, said signal generating elements for generating atarget generated signal upon being excited by electron beam energy, means for generating anv electron beam for scanning said target electrode, ymeans for establishing the intensity of said electron beam.. at a substantiallyv constant level during predetermined intervals, rsaid predetermined intervals being such as to substantially coincide in time with and occursubstantially only during excitation intervals.' during which said electron beam excites said signal generating elements, sensing means for sensingsaid target generated signal from said signal generating elements to 'form'anelectn'cal target generated signal, gating' means for` passing said electrical Vsignal substantially only during said .excitation intervals to 4form a gatev electrical-target" generated signal, and means for utilizing said gated electrical target generated signal to control said electron beam, said gating means comprising an electron discharge device, biasing means for biasing said electron discharge such as to prevent the flow of current in said electron discharge device, means for applying a gating signal to said electron discharge device to cause said electron discharge device to be conductive during said excitation intervals, and means for varying the current in said electron discharge device during said excitation interval according to said target generated signal.

4. A color television system comprising a target electrode having signal generating elements positioned thereon, said signal generating elements for generating a target generated signal upon being excited by electron beam energy, means for generating an electron beam for scanning said target electrode, means for establishing the intensity of said electron beam at a substantially constant level during predetermined intervals, said predetermined intervals being such as to substantially coincide in time with and occur substantially only during excitation intervals during which said electron beam excites said signal generating elements, sensing means for sensing said target generated signal from said signal generating elements to form an electrical target generated signal, gating means for passing said electrical signal substantially only during said excitation intervals to form a gated electrical target generated signal, and means for utilizing said gated electrical target generated signal to control said electron beam, said means for utilizing said gated electrical signal to control said electron beam comprising a plurality of sampling devices, said sampling devices being connected to means for modulating said electron beam, means for developing a plurality of sampling control signals from said gated electrical signal, and means for connecting said sampling control signals to said sampling devices.

5. A television system comprising a target electrode having a plurality of light producing elements and a plurality of signal generating elements, dilerent of said light producing elements for producing different component colors of light upon being excited by electron beam energy, said plurality of signal generating elements for producing a target generated signal upon being excited by electron beam energy during an excitation interval, means for generating an electron beam for scanning said target electrode, means for intensity modulating said electron beam, switching means adapted to receive different component color signals and a substantially unvarying signal, said switching means being connected to said modulating means such as to intensity modulate said electron beam sequentially by said color signals and said substantially unvarying signal, means for sensing said target generated signal, gating means adapted to receive said target generated signal for gating said target signal substantially only during said excitation interval to form a gated target generated signal, and means connecting said gated target generated signal to control said switching means such that said intensity modulation of said electron beam by said substantially unvarying signal substantially coincides in time with said excitation interval.v

6. A television system comprising a target electrode having a plurality of light producing elements and a plurality of signal generating elements, dilferent of said light producing elements for producing dilerent component colors of light upon being excited by electron beam energy during certain intervals of excitation, said plurality of signal generating elements for producing a target generated signal upon being excited by electron beam energy during other intervals of excitation, means for generating an electron beam for scanning said target electrode, means for intensity modulating said electron beam, switching means adapted to receive dilerent component color signals and a substantially unvarying signal, said switching means being connected to said modulating means such as to intensity modulate said electron beam sequentially by said color signals and said substantially unvarying signal during dierent intervals of modulation, means for sensing said target generated signal, gating means adapted to receive said target generated signal for gating said target generated signal substantially only during said other intervals of excitation to form a gated target generated signal, and means connecting said gated target generated signal to control said switching means such that particular of said intervals of modulation occur during said certain intervals of excitation.

References Cited in the le of this patent UNITED STATES PATENTS 2,674,651 Creamer Apr. 6, 1954 2,681,381 Creamer June 15, 1954 2,689,269 Bradley Sept. 14, 1954 2,736,764 Bingley Feb. 28, 1956 

